Brushless Motor Control Apparatus and Control Method and Motor System

ABSTRACT

A brushless motor control apparatus includes a mask processing unit to which digital induced voltage signal is input, a energizing current timing generation processing unit, a pulse width detection unit, and an advance angle correction unit for performing advance angle correction. The pulse width detection unit measures pulse width of spike voltage, and the advance angle correction unit calculates the correction to the advance angle according to the length of this pulse width. The energizing current timing generation processing unit takes half the value obtained after subtracting the correction value from the edge interval of the position detection signal generated in the mask processing unit as the advance angle.

TECHNICAL FIELD

The present invention relates to a brushless motor control apparatus,control method and motor system.

Priority is claimed on Japanese Patent Application No. 2005-107501 andthe Japanese Patent Application No. 2005-107502, both filed Apr. 4,2005, the contents of which are incorporated herein by reference.

BACKGROUND ART

Control apparatus of brushless motor controls the rotation of motorwhile switching the current energizing the stator coil wound in coilshape. The timing for switching the energizing current is determined bydetecting the magnetic pole position of the stator. In the conventionalcontrol apparatus of brushless motor, the position of rotation of rotorwas detected by obtaining the induced voltage generated in the statorcoil by the rotation of the rotor and no sensor for position detectionis installed separately from considerations of miniaturization of theentire system and so on. More specifically, the voltage at the neutralpoint of the stator coil and the induced voltage of the stator coil arecompared using the comparator, the variation time of output signal ofcomparator is measured, and the timing for switching the energizingcurrent to the stator coil is determined based on this variation time(for example, refer to Patent Document 1 below).

When the energizing current is switched and current becomes off, theflywheel current flows until the energy accumulated in the coil becomeszero, and the spike induced voltage (spike voltage) that occursconsequently is generated in the stator coil. For this reason, thecontrol apparatus must generate a mask signal, remove such spike voltageas noise, and judge the switching timing. The conventional method toremove spike voltage includes the method of detecting separately thevoltage drop between the control apparatus and the stator coil of thebrushless motor, generating a reset signal when this voltage dropreaches the same level as the standard voltage, and ignoring theposition detection only in the spike voltage space (for example, referto Patent Document 2 below). To generate a mask signal to mask the spikevoltage, means is available to switch on the mask signal when thegeneration of spike voltage is detected, and when a preset time setbeforehand has elapsed the mask signal is switched off (for example,refer to Patent Document 3 below).

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. S64-8890-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. H08-182379-   [Patent Document 3] Japanese Unexamined Patent Application, First    Publication No. H10-28395

The pulse width of the spike voltage in the control method described inPatent Document 1 increases with the increase in the current energizingthe stator coil; thus, the point of intersection of the induced voltageand the voltage at the neutral point was sometimes hidden by the spikevoltage, depending on the loading condition. In such cases, the positioncould not be detected, and the brushless motor suffered loss ofsynchronism.

Moreover, as described in Patent Document 2, to separately detect thevoltage drop, a bidirectional diode and bidirectional photocoupler,flip-flop circuit and so on are necessary, so that the problem becomesone of complicated configuration of the apparatus. Furthermore, asdescribed in Patent Document 3, when a mask signal is generated from thepulse of spike voltage, the problem becomes one in which the mask signalis not generated when spike voltage is not generated. In such cases,when spike voltage is generated when the energizing current is switchedsubsequently, this spike voltage cannot be eliminated, and it becomesdifficult to differentiate spike voltage and induced voltage waveforms.Consequently, the problem that occurred was that the position of therotor cannot be detected, and the timing for switching the currentenergizing the stator coil cannot be controlled.

DISCLOSURE OF INVENTION

This invention is made based on the considerations mentioned above. Theobject of the invention is to perform stable rotational control withoutinstalling a separate sensor in a brushless motor.

To resolve the problems mentioned above, a brushless motor controlapparatus according to a first aspect of the present invention isprovided with a drive circuit for obtaining a rotating magnetic field byenergizing a plurality of stator coils disposed so as to apply arotating magnetic field to the rotor having permanent magnet, and forsequentially switching the current energizing the stator coil based on aposition detection signal obtained by comparing the change in inducedvoltage generated in the stator coil not energized by rotation of therotor and the standard voltage, and a timing varying circuit forchanging the timing to switch the current energizing the stator coilaccording to the pulse width of induced voltage generated in the statorcoil immediately after switching the current energizing the stator coil.

This brushless motor control apparatus performs advance angle correctionof the position detection signal according to the pulse width of inducedvoltage occurring immediately after switching the energizing current.When the pulse width of induced voltage generated immediately afterswitching the energizing current becomes large, the current timing isspeeded up according to the pulse width, and the non-detection ofvoltage that becomes the standard because of being hidden in the pulsesof induced voltage generated immediately after switching the energizingcurrent is prevented.

In the brushless motor control apparatus of this first aspect, thetiming for switching the current energizing the stator coil may beadvanced only by half the pulse width of spike voltage generated due toflywheel current.

The brushless motor control apparatus performs advance angle correctionaccording to the pulse width of spike voltage as the induced voltageoccurring immediately after switching the energizing current. Morespecifically, by advancing only half the pulse width of the spikevoltage, if the pulse width of the spike voltage becomes large, theenergizing current timing is speeded up, and the non-detection ofvoltage that becomes the standard because of being hidden by the spikevoltage is prevented.

A motor system according to a first aspect of the present invention isprovided with the brushless motor control apparatus according to thefirst aspect mentioned above, and a brushless motor.

Based on the position detection signal generated by the controlapparatus, the current energizing each stator coil of the brushlessmotor is switched, and rotational control of the rotor is performed inthis motor system.

A brushless motor control method according to a first aspect of thepresent invention includes a process to obtain a rotating magnetic fieldby energizing a plurality of stator coils disposed so as to apply arotating magnetic field to a rotor having permanent magnet, a processfor sequentially switching the current energizing the stator coil basedon a position detection signal obtained by comparing the change ininduced voltage generated in the stator coil not energized by therotation of the rotor and the standard voltage, and a timing varyingprocess for changing the timing to switch the current energizing thestator coil according to the difference in the energizing currentswitching interval for the stator coil and the pulse width of theinduced voltage generated in the stator coil immediately after switchingthe current energizing the stator coil.

In the brushless motor control method, the difference between theinterval for switching the energizing current and the pulse width ofinduced voltage generated immediately after switching the energizingcurrent is obtained, and the timing for switching the energizing currentis advanced according to the magnitude of this difference.

The brushless motor control method according to the first aspectmentioned above, may include a process to stop measurement for only aperiod equivalent to the pulse width of the induced voltage generated inthe stator coil immediately after switching the current energizing thestator coil when the energizing current switching interval of the statorcoil is measured.

When obtaining the difference in the control method of this brushlessmotor, the timer and the like is stopped only for a period equivalent tothat of the pulse width of the induced voltage immediately afterswitching the energizing current so that the difference is obtainedwithout performing a subtraction. The timing for switching theenergizing current is advanced according to the magnitude of thedifference obtained in this way.

To resolve the problems mentioned above, the brushless motor controlapparatus according to a second aspect of the present invention isprovided with a drive circuit for obtaining a rotating magnetic field byenergizing a plurality of stator coils disposed so as to apply arotating magnetic field to a rotor having permanent magnet, and forsequentially switching the current energizing the stator coil based onthe position detection signal obtained by comparing the change in theinduced voltage generated in the stator coil not energized by therotation of the rotor and the standard voltage; and a mask signalgeneration unit for generating mask signal based on the positiondetection signal to mask the change in voltage generated in the statorcoil immediately after switching the current energizing the stator coil.

The brushless motor control apparatus generates the position detectionsignal indicated at the rotor position from the change in voltage of thestator coil, and generates a mask signal using this position detectionsignal. For this reason, mask signal is always generated regardless ofwhether spike voltage due to flywheel current is generated or not. Thus,the induced voltage signal required for position detection can beaccurately and stably extracted.

The mask signal in the brushless motor control apparatus according tothe second aspect mentioned above, may be generated before switching thecurrent energizing the stator coil.

Since the mask signal is already generated when the energizing currentis actually switched in the brushless motor control apparatus, spikevoltage due to the flywheel current can be correctly removed. As aspecific example, the timing for changing the energizing current isdetermined from the position detection signal, and the mask signal isgenerated before output of the command signal to switch the energizingcurrent.

The pulse width of the mask signal in the brushless motor controlapparatus of the second aspect mentioned above may be a fixed electricalangle.

The mask signal is generated beforehand for a fixed period only in thebrushless motor control apparatus. Therefore, comparison of the inducedvoltage signal required for position detection and the voltage thatbecomes a standard can be accurately made, and the position of the rotorcan be correctly detected.

The motor system according to a second aspect of the present inventionis provided with the brushless motor control apparatus according to thesecond aspect mentioned above, and a brushless motor.

Based on the position detection signal generated by the controlapparatus, the current energizing each stator coil of the brushlessmotor is switched, and rotational control of the rotor is performed inthis motor system. At this stage, the mask signal is generated based onthe position detection signal, and the spike voltage generated whenswitching the energizing current is eliminated.

The brushless motor control method according to a second aspect of thepresent invention includes a process for obtaining a rotating magneticfield by energizing a plurality of stator coils disposed so as to applya rotating magnetic field to a rotor having permanent magnet, and forsequentially switching the current energizing the stator coil based onthe position detection signal obtained by comparing the change in theinduced voltage generated in the stator coil not energized by therotation of the rotor and the standard voltage; and a process forgenerating a mask signal based on the position detection signal and formasking the change in the voltage generated in the stator coilimmediately after switching the current energizing the stator coil.

This brushless motor control method generates the position detectionsignal indicating the rotor position, controls the brushless motor basedon this position detection signal, and feeds back this positiondetection signal for generating the mask signal. For this reason, masksignal is always generated regardless of whether spike voltage due toflywheel current is generated or not; thus, the induced voltage signalrequired for position detection can be accurately and stably acquired.

According to the first aspect of the present invention, advance anglecorrection can be performed according to the pulse width of the inducedvoltage generated immediately after switching the energizing current.Therefore, when the pulse width of the induced voltage immediately afterswitching the energizing current increases due to the increase in loadin the brushless motor, the timing for switching the energizing currentwill be corrected for advance angle accordingly, and comparison betweenthe voltage that becomes the standard and the induced voltage can bemade. Consequently, signal for detection the position of the rotor canbe accurately obtained even if load variation occurs, and as a result,loss of synchronism of the brushless motor can be prevented.

Also, according to the second aspect of the present invention, the masksignal is generated using the position detection signal used inswitching the current energizing the stator coil; so that the masksignal can be generated regardless of whether the spike voltage due tothe flywheel current is generated or not generated. Consequently, theinduced voltage signal required for position detection, and the signalof spike voltage to be eliminated can be correctly differentiated, theposition of the rotor can be accurately detected, and loss ofsynchronism of the brushless motor can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that shows the motor system including thebrushless motor control apparatus according to a first embodiment of thepresent invention.

FIG. 2 shows the induced state of the stator and the rotor, and theenergizing current pattern of the brushless motor used in the presentinvention.

FIG. 3 is an explanatory drawing of the signal processing of inducedvoltage waveform of the stator coil in the first embodiment of thepresent invention, and is also a timing chart showing the procedure forgenerating a digital signal from an analog signal.

FIG. 4 is an explanatory drawing of the signal processing of inducedvoltage waveform of the stator coil in the first embodiment of thepresent invention and the procedure for generating mask signal, and isalso a timing chart showing the procedure for generating a positiondetection signal after mask processing.

FIG. 5 is a timing chart showing the signal of induced voltage waveformof the stator coil at heavy load and when the rpm has increased in thefirst embodiment of the present invention.

FIG. 6 is a timing chart showing the signal of the induced voltagewaveform of the stator coil after advance angle correction has beenperformed from the state in FIG. 5, in the first embodiment of thepresent invention.

FIG. 7 is a block diagram that shows the motor system including thebrushless motor control apparatus according to a second embodiment ofthe present invention.

FIG. 8 is a block diagram that shows the motor system including thebrushless motor control apparatus according to a third embodiment of thepresent invention.

FIG. 9 is an explanatory drawing of the signal processing of inducedvoltage waveform of the stator coil in the third embodiment of thepresent invention, and is also a timing chart showing the procedure forgenerating a digital signal from an analog signal.

FIG. 10 is an explanatory drawing of the signal processing of inducedvoltage waveform of the stator coil in the third embodiment of thepresent invention and the procedure for generating a mask signal, and isalso a timing chart showing the procedure for generating a positiondetection signal after mask processing.

FIG. 11 is a timing chart that explains the judgment processing ofinduced voltage edge in the third embodiment of the present invention,and also shows the case when the pulse width of the spike voltage isbelow the pulse width of the mask signal.

FIG. 12 is a timing chart that explains the judgment processing ofinduced voltage edge in the third embodiment of the present invention,and also shows the case when the pulse width of the spike voltageexceeds the pulse width of the mask signal.

FIG. 13 is a timing chart that explains the judgment processing ofinduced voltage edge in the third embodiment of the present invention,and it explains the judgment processing during an overload.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the invention will be describedhereinafter in detail referring to the drawings.

FIG. 1 shows the schematic configuration of motor system includingbrushless motor. This motor system is provided with brushless motor 1,and drive device 2 of the brushless motor 1, such that energizingcurrent control is performed from power source 3 through the drivedevice 2.

As shown in FIG. 2, the main components of the brushless motor 1 are astator 5 and a rotor 6. The stator is wound with three stator coils U, Vand W which are so called star-connected. The rotor 6 includes arotating shaft and permanent magnets wherein a plurality of magneticpoles (north pole and south pole) are disposed in the circumferentialdirection of the rotating shaft. The brushless motor 1 may be aninner-rotor type or outer-rotor type brushless motor.

As shown in FIG. 1, each of the stator coils U, V, W of the brushlessmotor 1 is drawn out of the brushless motor 1 and connected to the drivedevice 2. The drive device 2 has a control apparatus 10 that performs aspecified process according to the input of the drive signal. The outputof the control apparatus 10 is connected to the three-phase inverter 12through the pre-driver 11. The three-phase inverter 12 is connected tothe power source 3, and is configured such that the stator coils U, V, Ware energized according to the output of the control apparatus 10. Also,the analog waveform of induced voltage that appears in each of thestator coils U, V, W by the current from the three-phase inverter 12energizing the brushless motor 1 becomes the input to the inducedvoltage I/F (interface circuit 14 after the voltage drops in the voltagedividing circuit 13. The induced voltage I/F circuit 14 generates theelectric potential of the neutral point of the star connection as thestandard voltage (equivalent neutral point voltage) from the voltage(induced voltage) of each of the stator coils U, V, W. The waveform ofthe induced voltage of each of the stator coils U, V, W, and theequivalent neutral point voltage are input to each of the comparators soas to generate digital signals. The output of each comparator isconnected to the control apparatus 10.

The functions of the control apparatus 10 may be divided among the startprocessing unit 21 into which the drive signal is input, the maskprocessing unit 22 connected to the induced voltage I/F circuit 14, theenergizing current timing generation processing unit 23 that receivesthe specified data from the mask processing unit 22, the pulse widthdetection unit 24, and the advance angle correction unit 25 thatperforms the processes following the pulse width detection unit 24. Datacan be input from the start processing unit 21 and the advance anglecorrection unit 25 in addition to the mask processing unit 22 to theenergizing current timing generation processing unit 23. The output ofthe energizing current timing generation processing unit 23 is connectedto the pre-driver 11. This kind of control apparatus 10, may be realizedfor example, by a single-chip micro-computer.

The functions of the mask processing unit 22 may be classified as anedge detection device 30 that detects the changes in the induced voltagesignals of stator coils U, V, W; a state detection device 31 thatdetects the state of the induced voltage of the stator coils U, V, Wfrom the magnitude of the voltage level; and a mask signal generatingdevice 32 that generates a mask signal based on the results of detectionof the edge detection device 30 and the state detection device 31. Theoperations of each of these devices are described hereafter.

Next, the operations of this embodiment are described below.

First, referring to FIG. 2, the relationship between the pattern ofenergizing current flowing from the drive device 2 to the brushlessmotor 1 and the induction state of stator 5 and rotor 6 of the brushlessmotor 1 is described first. FIG. 2 illustrates a 120°-rectangular waveenergizing current drive operation using an interlocking-type brushlessmotor.

As shown in FIG. 2, there are six energizing current patterns (#1 to #6)obtained by combining the three stator coils U, V, and W. The energizingcurrent pattern #1 flows from stator coil W to stator coil V. The stator5 and the rotor 6 change to the induction state shown in pattern [A] isobtained when the energizing current pattern is switched to energizingcurrent pattern #1. When the energizing current pattern #1 is sustained,pattern [B] shows the state when torque has occurred in rotor 6 and ithas rotated through an electrical angle of 30° from the position ofpattern [A] in the CCW direction. At this stage, the center of thestator coil W (open phase) and the center of the south pole of the rotor6 are physically opposite to each other. Electrically, the state is anintersection of the equivalent neutral point voltage and the inducedvoltage. This kind of state is taken as the timing to detect theposition of rotation of the rotor 6. Moreover, pattern [C] is the statewhen the rotor 6 has rotated by an electrical angle of 30° from thepattern [B]. This pattern [C] indicates the instant the energizingcurrent pattern #2 has been switched. Thus, if the energizing currentpattern is switched at the timing at which the rotor 6 has rotated by anelectrical angle of only 30° from the timing at which the position ofrotation of rotor 6 was detected, then the rotor 6 can be rotated by therotating magnetic field generated by the stator coils U, V and W. If theenergizing current patterns #1 to #6 are switched sequentially this way,then the rotor 6 rotates with respect to stator 5 as the induction statemoves sequentially from pattern [A] to pattern [L]. Patterns [B], [D],[F], [H], [J], [L] indicate the timings for detecting all the positionsof rotation of rotor 6, and the torque generated at this stage is themaximum torque.

Here, the handling of the brushless motor 1 at the start is described.In the brushless motor 1 with no position detection sensor, the positionof the rotor 6 at start cannot be identified. Thus, the energizingcurrent timing generation processing unit 23 is controlled (initialoperation) such that the start processing unit 21 outputs the specifiedenergizing current pattern for a fixed period of time. As a result, therotor 6 is locked at a position matching its energizing current pattern,and the initial position of the rotor 6 is established. For example, ifthe energizing pattern #5 is implemented as the initial operation, therotor 6 is locked at the position indicated by pattern [M], and as aresult, the initial position is established. For the sustaining time atthis stage, the value set beforehand corresponding to the physical frameof the brushless motor 1 or the inertia load is used. Subsequently, theenergizing pattern after skipping one pattern following the existingenergizing pattern is implemented (skipped energizing pattern). In theprevious example, the next pattern after the energizing pattern #5should be pattern #6, but since a skipped energizing pattern is to beimplemented, the energizing pattern #1 will be implemented. The reasonfor skipping the energizing pattern #6 is that even if the energizingpattern #6 is implemented, because the position of the pattern [J] atwhich the maximum torque at the locked position of the pattern [M] canbe obtained, has already been crossed, the induced voltage at themaximum torque, which becomes the position data, cannot be obtained.Consequently, by implementing pattern #1, the same torque is generatedas when moving from pattern [M] to pattern [A] and from pattern [L] topattern [A]. In this way, when the induced voltage reaches a constantlevel after the rotor 6 is rotated and the position data is obtained,the usual operation can be continued as-is and feedback control can beperformed. In contrast, when the induced voltage has not reached aconstant level, the position data cannot be obtained; therefore, afterimplementing the initial operation with the energizing pattern #1, theskipped energizing pattern is implemented with energizing pattern #3.Thereafter, a similar procedure is repeated until the normal operationis enabled.

Next, the control of energizing current during normal operation isdescribed referring mainly to FIG. 1, FIG. 3 and FIG. 4.

In FIG. 3, the electrical angle is taken on the horizontal axis, theenergizing current state of each stator coil U, V, W from the upper sideis taken on the vertical axis. The actual induced voltage waveforms Uv,Vv, Wv (analog signal) of each stator coil U, V, W and the inducedvoltage signals Ud, Vd, Wd (digital signal) of each stator coil are alsoillustrated. The state of energizing of each stator coil U, V, W of theuppermost stage shows that the stator coils U, V, W affixed with “+” tothe upper stage, are on the high potential side, while the stator coilsU, V, W with “−” affixed to the lower stage are on the low potentialside. That is, “W+” and “V−” between the electrical angles of 0° and 60°indicate energizing from the stator coil W to the stator coil V(equivalent to the energizing pattern #1 in FIG. 2). Moreover, theinduced voltage waveforms Uv, Vv, Wv are illustrated by superimposingthe equivalent neutral point voltage as virtual line. Furthermore, forexample, the pulse that starts up with an electrical angle of 0°, or thepulse that starts up with an electrical angle of 180° is a spike voltagein the induced voltage waveform Uv; these spike voltages are signalsthat are to be removed in this embodiment.

The induced voltage waveforms Uv, Vv, Wv of the stator coils U, V, W areinput to the induced voltage I/F circuit 14 (see FIG. 1). The equivalentneutral point voltage can be obtained from these voltage values. If thisequivalent neutral point voltage and the induced voltage waveform Uv areinput to the comparator, the induced voltage signal Ud can be obtained.Similarly, the induced voltage signals Vd, Wd, which are digitalsignals, can be obtained from the induced voltage waveforms Vv, Vw,which are analog signals and from the equivalent neutral point voltage.These induced voltage signals Ud, Vv, Wv are input to the maskprocessing unit 22 of the control apparatus 10, and the mask signal isgenerated.

FIG. 4 is a schematic diagram showing the generation process of the masksignal and the generation process of the position detection signal. InFIG. 4, the electrical angle is taken on the horizontal axis, and fromthe upper side, the induced voltage signal Ud, Vd, Wd of each statorcoil U, V, W, and the mask signal Um for stator coil U, the mask signalVm for the stator coil V, the mask signal Wm for the stator coil W, andthe position detection signals Us, Vs, Ws of each stator coil U, V, Wafter masking, and the position detection signals Uss, Vss, Wss afterelectrical angle 30° phase shift are sequentially illustrated on thevertical axis.

When the three induced voltage signals Ud, Vd, Wd are input, the maskprocessing unit 22 of the control apparatus 10 detects the leading edgeand the trailing edge of each induced voltage signal Ud, Vd, Wd with theedge detection device 30. Similarly, the voltage levels of each of theinduced voltage signals Ud, Vd, Wd are detected with the state detectiondevice 31. The results of detection by the edge detection device 30 andthe state detection device 31 are input to the mask signal generatingdevice 32. The mask signal generating device 32 generates the masksignal while referring to the mask signal generating conditionsregistered beforehand in memory.

Table 1 summarizes the specific examples of mask signal generatingconditions.

TABLE 1 Induced Voltage Signal Mask Signal Condition Ud Vd Wd Um Vm WmC1 H L ↑ L* L→H(↑) H→L(↓) C2 L H ↓ L* L→H(↑) H→L(↓) C3 L ↑ H L→H(↑)H→L(↓) L* C4 H ↓ L L→H(↑) H→L(↓) L* C5 ↑ H L H→L(↓) L* L→H(↑) C6 ↓ L HH→L(↓) L* L→H(↑)

The conditions C1 to C6 in Table 1 indicate the mask signal generatingconditions. For example, in condition C1, if the induced voltage signalWd is the leading edge (T), the induced voltage signal Ud is H (High),and the induced voltage signal Vd is L (Low), the mask signal Wm for thestator coil W is changed from L level to H level, and the mask signal Umis maintained at the L level. Furthermore, the mask signal Wm is changedfrom the H level to the L level. Here, the “*” in Table 1 indicates thatthe level is maintained. Similarly, condition C2 indicates the conditionwhen the induced voltage signal Wd is a trailing edge (i).

Detailed examples of processing by the mask processing unit 22 are givenbelow. When the electrical angle increases from 0° in FIG. 4, thetrailing edge that rapidly goes from H level to L level with the inducedvoltage signal Ud initially, is detected by the edge detection device25. The signal indicating that it is the trailing edge of the inducedvoltage signal Ud is output to the mask signal generating device 27. Atthe same time, information indicating the voltage levels of each of theinduced voltage signals Ud, Vd, Wd is input from the state detectiondevice 26 to the mask signal generating device 27. Consequently, themask signal generating device 27 examines the induced voltage levels ofthe remaining two stator coils V, W when the induced voltage signal Udis taken as the induced voltage of the specific stator coil U. In thiscase, the induced voltage Vd is at the L level while the induced voltageWd is at the H level. This state corresponds to the condition C6 inTable 1. Thus, the mask signal Wm for the stator coil W is set at the Hlevel, while the mask signal Um for the stator coil U is set at the Llevel.

Moreover, the mask signal Vm for the stator coil V is maintained at theL level.

Next, for an electrical angle of 30°, the leading edge of the inducedvoltage signal Ud can be detected, but since the level of inducedvoltage signal Vd, Wd does not satisfy the condition C5, the settings ofmask signals, Um, Vm and Vm do not change. Similarly, the trailing edgeof the induced voltage signal W of the electrical angle of 60° does notsatisfy the condition C2; thus, the settings of mask signal Um, Vm, Wmdo not change. The leading edge of the induced voltage signal W thatappears between the electrical angles of 60° and 90° satisfies thecondition C1; therefore, the mask signal Vm is set to H, and the masksignal Wm is set to the L level. Moreover, the mask signal Um is set tothe L level. As a result, the mask signal Wm becomes the mask of thepulse width corresponding to the electrical angles from the condition C6to the condition C1.

In a similarly way, the mask signals Um, Vm, Wm are generated. The masksignal Um includes pulse that rises with the condition C4 and pulse thatfalls with the condition C5, and pulse that rises with the condition C3and falls with the condition C6. The mask signal Vm includes pulse thatrises with the condition C1 and pulse that falls with the condition C4,and pulse that rises with the condition C2 and falls with the conditionC3. The mask signal Wm includes pulse that rises with the condition C6and pulse that falls with the condition C1, and pulse that rises withthe condition C5 and falls with the condition C2.

While the mask signal Um is in the H level, and if the changes in theinduced voltage waveform Uv are ignored, then the position detectionsignal Us can be obtained. Similarly, the position detection signal Vscan be obtained from the mask signal Vm and the induced voltage Vv, andthe position detection signal Ws can be obtained from the mask signal Wmand the induced voltage Wv. These position detection signals Us, Vs, Wsare output from the mask processing unit 22 to the energizing currenttiming generation processing unit 23. The energizing current timinggeneration processing unit 23 advances the phase of each of the positiondetection signals Us, Vs, Ws by electrical angle 30° only, and generatesthe position detection signals Uss, Vss and Wss. These positiondetection signals Uss, Vss, Wss are equivalent to the signals obtainedwhen a position detection sensor is installed. The energizing currenttiming generation processing unit 23 controls the switching timing ofthe current energizing each of the stator coils U, V, W, based on theposition detection signals Uss, Vss, Wss. The result is that the rotor 6of the brushless motor 1 rotates, as shown in FIG. 2.

Moreover, operation at heavy loading and the state of increase in therpm are shown in FIG. 5. In FIG. 5, the electrical angle is taken on thehorizontal axis, while the induced voltage waveforms Uv, Wv of thestator coils U, W, the position detection signals Us, Ws after maskingthe stator coils U, W, and the position detection signal Uss afteradvance angle correction are shown sequentially from the upper side ofthe vertical axis. In FIG. 5, only two-phase parts generatedcontinuously by the energizing current switching timing are illustratedfrom the three stator coils U, V, W. The processing of these two phaseswill be explained below but it is to be noted that the invention is notlimited to the combination of two phases. In the induced voltagewaveforms Uv, Wv shown in FIG. 5 the waveforms of rated induced voltageare shown in broken line, while the waveform of induced voltage duringheavy load is illustrated by bold line.

The pulse width Tp of the spike voltage becomes large in FIG. 5, and itstrailing edge approaches the intersection of the equivalent neutralpoint and the induced voltage. If the pulse width Tp becomes larger thanthis and the intersection of the equivalent neutral point and theinduced voltage becomes hidden by the spike voltage, the generation ofthe induced voltage signals Ud, Vd, Wd can no longer be implemented andposition detection is not possible. In this way, if the pulse width ofthe spike voltage becomes larger than during steady-state operation,advance angle correction is implemented by the pulse width detectionunit 24 and the advance angle correction unit 25, and the energizingcurrent timing generated by the energizing current timing generationprocessing unit 23 is changed.

First, the mask processing unit 22 masks the spike voltage and generatesthe position detection signals Us, Ws, similar to the procedurementioned earlier. The mask processing unit 22 hands over the positiondetection signals Us, Ws, to the energizing current timing generationprocessing unit 23, and hands over the induced voltage signals Ud, Wd tothe pulse width detection unit 24. The pulse width detection unit 24counts the pulse width Tp of the spike voltage, and hands over the countvalue to the advance angle correction unit 25. The advance anglecorrection unit 25 calculates half the value of the pulse width Tp, andhands it over to the energizing current timing generation processingunit 23 as the advance angle correction value. A detailed example ofprocessing to half the value is the 1-bit shift of the count value ofthe pulse width Tp.

The energizing current timing generation processing unit 23 counts theedge interval Te of the position detection signal Us and the positiondetection signal Ws, as the energizing current switching interval, andcalculates the value of half this edge interval. A detailed example ofprocessing to half the value is the 1-bit shift of the count value ofthe edge interval Te. The advance angle correction value (half the valueof the pulse width Tp) is subtracted from half the value of the edgeinterval, and the calculated result (=(½)×Te−(½)×Tp) is taken as thephase shift amount θ. The position detection signals Us, Vs, Ws of eachof the stator coils U, V, W are taken as position detection signalsUss′, Vss′, Wss′ advanced by only the phase shift amount θ. The currentenergizing each of the stator coils U, V, W is switched according tothese position detection signals Uss′, Vss′ and Wss′.

The results after performing the advance angle correction in this way,are shown in FIG. 6. In FIG. 6 the advance angle is taken on thehorizontal axis, while the induced voltage waveforms, Uv, Wv afteradvance angle correction, and the induced voltage signals Ud, Wd arearranged sequentially on the vertical axis. For comparison, the positiondetection signals Uss, Wss before the advance angle correction and thedetection signals Uss′ after the advance angle correction are alsoillustrated on the vertical axis. Similarly, signals after advance anglecorrection are generated for the position detection signals Vss′, Wss′not illustrated in the figure above.

By advancing all the induced voltage waveforms Uv, Wv, the equivalentneutral point will be positioned at the center of the area in which theinduced voltage varies with a substantial inclination. Accordingly, evenif the pulse width Tp of the spike voltage is increased by increasingthe load or the speed from this state, the intersection of theequivalent neutral point and the induced voltage is not likely to behidden, so the position detection can be continuously performed. Asshown in FIG. 6, the advance angle of the waveform finally becomes Tp/2,that is, half the pulse width of the spike voltage occurring in theflywheel voltage.

According to this embodiment, the timing varying device is constitutedby the energizing current timing generation processing unit 23, thepulse width detection unit 24 and the advance angle correction unit 25,and advance angle correction of the position detection signal isperformed using the pulse width Tp of the spike voltage. Therefore, evenif the pulse width Tp of the spike voltage increases when the load inthe brushless motor 1 increases or the rpm increases, the intersectionof the equivalent neutral point voltage and the induced voltagewaveforms Uv, Vv, Wv can be correctly acquired. For this reason, thespike voltage is properly masked by the mask signals Um, Vm, Wmgenerated from the induced voltage waveforms Uv, Vv, Wv, and theposition detection signals Us, Vs and Ws can be generated. Consequently,the position detection signals Uss′, Vss′, Wss′ can be properlygenerated without depending on the rpm or the load, and the ability toresist loss of synchronism of the brushless motor 1 can be enhanced.

Next, a second embodiment of the present invention is described below.Only the arithmetic processing of the advance angle varies in thisembodiment; other components and operations are the same as in the firstembodiment.

As shown in FIG. 7, the functions of the control apparatus 40 can bedivided among the start processing unit 21, the mask processing unit 22,the energizing current timing generation processing unit 23, the pulsewidth detection unit 24, and the advance angle calculation unit 41. Theadvance angle calculation unit 41 is configured to accept data inputfrom the mask processing unit 22 and the pulse width detection unit 24,to calculate the advance angle, and to output it to the energizingcurrent timing generation processing unit 23.

Next, the operations of this embodiment are described here. First, theadvance angle calculation unit 41 receives the position detectionsignals Us, Vs, Ws after masking from the mask processing unit 22, andalso receives the count value of the pulse width Tp of the spike voltagefrom the pulse width detection unit 24. Next, the advance anglecalculation unit 41 counts the edge intervals of the position detectionsignals Us, Ws, subtracts the pulse width Tp from this count value andcalculates half of this amount. The result is that the same phase shiftamount θ as the first embodiment is obtained. This phase shift amount θis output to the energizing current timing generation processing unit23. The energizing current timing generation processing unit 23 advancesthe position detection signals Us, Vs, Ws by only the phase shift amountθ, generates the position detection signals Uss′, Vss′, Wss′, andswitches the timing of the energizing current from the three-phaseinverter 12.

Also, the advance angle calculation unit 41 may stop the counter ortimer of the edge interval Te by only the pulse width TP instead ofsubtracting the pulse width Tp from the edge interval Te. In this case,the advance angle calculation unit 41 receives the position detectionsignals Us, Vs, Ws after masking and the induced voltage signals Ud, Vd,Wd from the mask processing unit 22, and also receives the count valueof the pulse width Tp of the spike voltage from the pulse widthdetection unit 24. Next, the advance angle calculation unit 41 stops thecounter or timer for measurement of the edge interval Te for a period ofonly the pulse width Tp. As a result, if the obtained count value ishalved, the shift phase amount θ can be obtained.

Furthermore, to explain the process here in more detail, the advanceangle calculation unit 41 stops the counter or the timer only for theperiod the conditional equation (1) is satisfied.

((Ud̂Us)|(Vd̂Vs)|(Wd̂Ws))=1  (1)

Here, “̂” indicates the logical operator “EXOR” while “|” indicates thelogical operator “OR.” This conditional equation (1) is saved in memorybeforehand. For example, when counting the edge interval Te, the counteror the timer is stopped only for the interval the high and low voltagelevels are reversed ((Ud̂Us)=1) between the induced voltage signal Ud andthe position detection signal Us after masking. The period thiscondition is satisfied is equivalent to the pulse width Tp of the spikevoltage; therefore, if half this count value is acquired, the shiftphase amount θ can be obtained.

According to this embodiment, the timing varying device is constitutedby the energizing current timing generation processing unit 23, thepulse width detection unit 24 and the advance angle calculation unit 41.By stopping the counter or the timer for measuring the period ofrotation of say the edge interval when deciding the amount of advance,by only the pulse width of the spike voltage, the advance amount can bedetermined. Therefore, the circuit configuration and the process can besimplified compared to the case when the edge interval and the pulsewidth are separately counted and these values are calculated after theyare stored.

The other effects are the same as those for the first embodiment.

In the above-mentioned embodiment, the mask signals Um, Vm, Wm may begenerated based on the position detection signals Uss, Vss, Wss whenswitching the current energizing the stator coils U, V, W and on theposition detection signals Uss′, Vss′, Wss′. The pulse width of the masksignal may be of a magnitude corresponding to the preset electricalangle.

Next, the third embodiment of the present invention is described belowin detail referring to the drawings. The same reference numbers areaffixed to the same configuration elements as in the first and thesecond embodiments; so their explanations are omitted here.

In the motor system including the brushless motor related to the thirdembodiment indicated in FIG. 8, the configuration of the controlapparatus 110 differs from that in the first embodiment.

The functions of the control apparatus 110 can be classified as thestart processing unit 121 to which the drive signal is input; the edgeseparation processing unit 122 connected to the induced voltage I/Fcircuit 14, the rotor position detecting unit 123 that generates thesignal to detect the rotating position of the rotor 6; the stopprocessing unit 124 that performs processing during an overload, theenergizing current switching timing generation unit 125, and the masksignal generation unit 126 that generates the mask signal to remove thespike voltage. Signals are output from the edge separation processingunit 122 to the rotor position detecting unit 123 and the stopprocessing unit 124. Signals are output from the rotor positiondetecting unit 123 to the stop processing unit 124 and the energizingcurrent switching timing generation unit 125. Moreover, signals areoutput from the start processing unit 121 and the stop processing unit124 to the energizing current switching timing generation unit 125.Signals are fed back to the edge separation processing unit 122 throughthe mask processing unit 126 from the energizing current switchingtiming generation unit 125 so that finally the information on switchingtiming is output to the pre-driver 11. The functions of each part aredescribed here in detail. This kind of control apparatus 110, may berealized for example, by a single-chip micro-computer.

Next, the operations of this embodiment are described here.

The relationship between the energizing current pattern energizing thebrushless motor 1 from the drive device 2 and the induction state of thestator 5 and rotor 6 of the brushless motor 1 is the same as describedusing FIG. 2.

The handling of the brushless motor 1 at start is performed bycontrolling (initial operation) the energizing current timing generationprocessing unit 125 such that the start processing unit 121 outputs thespecified energizing current pattern at a fixed time. As a result, therotor 6 is locked at a position matching its energizing current pattern,and the initial position of the rotor 6 is established. Subsequently,the handling of the brushless motor 1 at start is similar to theprocedure described for the first embodiment. The switching timing ofthe energizing current at start may be generated by analog-typesynchronizing operation.

Next, the control of energizing current during normal operation isdescribed referring mainly to FIG. 8, FIG. 9 and FIG. 10.

In FIG. 9, the electrical angle is taken on the horizontal axis, theenergizing current state of each stator coil U, V, W, the actual inducedvoltage waveforms Uv, Vv, Wv (analog signals) of each stator coil U, V,W and the induced voltage signals Ud, Vd, Wd (digital signal) of eachstator coil U, V, W are also illustrated from the upper side on thevertical axis. The state of energizing of each stator coil U, V, W ofthe uppermost stage shows that the stator coils U, V, W affixed with “+”to the upper stage, are on the high potential side, while the statorcoils U, V, W with “−” affixed to the lower stage are on the lowpotential side. That is, “W+” and “V−” between the electrical angles of0° and 60° indicate energizing from the stator coil W to the stator coilV (equivalent to the energizing pattern #1 in FIG. 2). Furthermore, forexample, the pulse that starts up with an electrical angle of 0°, or thepulse that starts up with an electrical angle of 180° is a spike voltagePs in the induced voltage waveform Uv. These spike voltages Ps aresignals that are to be removed in this embodiment.

FIG. 10 is a schematic diagram showing the generation process of themask signal and the generation process of the position detection signal.In FIG. 10, the electrical angle is taken on the horizontal axis, whilethe induced voltage signals Ud, Vd, Wd (same signals as in FIG. 9) ofeach of the stator coils U, V, W, the position detection signals Us, Vs,Ws of the stator coils U, V, W, and the position detection signals Uss,Vss, Wss after a 30° electrical angle phase shift, the mask signal Umfor the stator coil U, the mask signal Vm for the stator coil V, and themask signal Wm for the stator coil W are sequentially displayed from theupper side on the vertical axis.

The induced voltage waveforms Uv, Vv, Wv of each of the stator coils U,V, W shown in FIG. 9 are input to the induced voltage I/F circuit 14(see FIG. 8), and the equivalent neutral point voltage is obtained fromthese voltage values. If this equivalent neutral point voltage and theinduced voltage waveform Uv are input to the comparator, the inducedvoltage signal Ud can be obtained. Similarly, the induced voltagesignals Vd, Wd of the digital signal can be obtained from the inducedvoltage waveforms Vv, Wv of the analog signal. These induced voltagesignals Ud, Vv, Wv are input to the edge separation processing unit 122of the control apparatus 110, and the energizing current switchingtiming is generated by the process described below.

First, the edge separation processing unit 122 separates the inducedvoltage edge generated by the rotation of the rotor 6 and the edge ofthe spike voltage Ps from the pulse signals of the induced voltagesignals Ud, Vv, Wv. The rotor position detecting unit 123 generates theposition detection signals Us, Vs, Ws from the information of inducedvoltage generated by rotating the rotor 6, and hands it over to theenergizing current switching timing generation unit 125. The energizingcurrent switching timing generation unit 125 counts the interval Te ofthe edge (induced voltage edge) of the position detection signals Us,Vs, Ws shown in FIG. 10. Specifically, the counter starts measurement ofall the edges of the position detection signals Us, Vs, Ws as triggers;next, when the edge of any of the position detection signals Us, Vs, Wsis detected and the count value is cleared, the next count startssimultaneously. While the brushless motor 1 is rotating, the inducedvoltage edge interval Te is generated for each electrical angle of 60°,therefore the rotational speed and acceleration of the rotor 6 (see FIG.2) are calculated from the count value showing the generated interval ofthe induced voltage, according to which the energizing current switchingtiming is estimated; a part proportional to this is phase shifted in thephase of position detection signals Us, Vs, Ws, and the phase detectionsignals Uss, Vss, Wss are generated. The control apparatus 110 controlsthe three-phase inverter 12 according to these phase detection signalsUss, Vss, Wss, and rotates the rotor 6 of the brushless motor 1 byswitching the current energizing each of the stator coils U, V and W.

Here, the energizing current switching timing generation unit 125outputs the signal commanding the switching of energizing current to thethree-phase inverter 12, and at the same time outputs the positiondetection signals Us, Vs, Ws to the mask signal generation unit 126immediately in front. The mask signal generation unit 126 receives theinput of this position detection signal Us, Vs, Ws and generates themask signal Um, Vm, Wm. For example, in the example shown in FIG. 10,the mask signal Wm of the stator coil W is set to the H (High) level atthe generated timing equivalent to that of a specified electrical anglefrom the timing of the induced voltage edge of the position detectionsignal Us of the stator coil U. Similarly, the mask signal Um of thestator coil U is set to the H (High) level at the generated timingequivalent to that of a specified electrical angle from the timing ofthe induced voltage edge of the position detection signal Vs of thestator coil V. The mask signal Vm of the stator coil V is set to the H(High) level at the generated timing equivalent to that of a specifiedelectrical angle from the timing of the induced voltage edge of theposition detection signal Ws of the stator coil W. The signal level ofeach of these mask signals Um, Vm, Wm after maintained for a specifiedelectrical angle are changed to a L (Low) level. The mask signals Um,Vm, Wm are input to the edge separation processing unit 122.

The electrical angle that decides the pulse width of the mask signalsUm, Vm, Wm always calculates the angle saved in the memory beforehandfrom the measured value of Te. More specifically, a value larger thanthe pulse width of the spike voltage PS when rotated at the normal load,and which does not mask the intersection of the induced voltagewaveforms Uv, Uv, Wv and the equivalent neutral point voltage with thepulse of the mask signal, and where 0°<θ<30° is used.

Subsequently, the pulse of the spike voltage Ps is removed by the masksignals Um, Vm, Wm corresponding to the induced voltage signals Ud, Vd,Wd input from the induced voltage I/F circuit 14, the position detectionsignals Us, Vs, Ws are generated, and the energizing current of thebrushless motor 1 is controlled.

Here, the pulse width of the spike voltage Ps varies according to themagnitude of the load and the rotational speed. In contrast, the masksignals Um, Vm, Wm have constant pulse widths, so the pulse of the spikevoltage Ps may be completely masked, or may not be masked by the masksignals Um, Vm, Wm. The processing of the edge separation processingunit 122 in these cases are described sequentially below.

First, when the pulse width of the spike voltage Ps is lower than themask width, both the starting edge and the ending edge of the spikevoltage Ps can be masked, as shown in FIG. 11. In this case, the rotorposition detecting unit 123, generates the position detection signalsUs, Vs, Ws from the induced voltage signals Ud, Vd, Wd, according to theinduced voltage signal detection logic, as shown in Table 2.

TABLE 2 Level to be checked Edge to be detected Ud Vd Wd Leading edge Ud— L H Vd H — L Wd L H — Trailing edge Ud — H L Vd L — H Wd H L —

The leading edge and the trailing edge of the spike voltage Ps startingfrom the electrical angle θ1 in FIG. 11 are ignored since the masksignal UM is at the H level. The leading edge in the electrical angle θ2satisfies the condition for induced voltage signal Ud of the leadingedge of Table 2; therefore, it can be treated as the leading edge of theinduced voltage of the stator coil U. Similarly, the trailing edge andthe leading edge of the spike voltage Ps starting from the electricalangle θ3 can be ignored because the mask signal Um is at the H level.The trailing edge of the induced voltage signal Ud in the electricalangle θ4 satisfies the condition for the induced voltage signal Ud ofthe trailing edge of Table 2; therefore, it can be treated as thetrailing edge of the induced voltage of the stator coil U. In the sameway, for the other induced voltage signals Vd, Wd also, the leading edgeand the trailing edge of the induced voltage can be judged according tothe induced voltage signal detection logic of Table 2, and the positiondetection signals Us, Vs and Ws can be generated.

In contrast, as shown in FIG. 12, when the pulse width of the spikevoltage Ps exceeds the mask width, the starting edge of the spikevoltage Ps can be masked, but the ending edge of the spike voltage Pscannot be masked. In such cases, the rotor position detecting unit 123separates the induced voltage edge referring to the spike voltage endingedge judgment logic as shown in Table 3, in addition to the inducedvoltage signal detection logic as shown in Table 2, and generates theposition detection signals Us, Vs, Ws.

TABLE 3 Level to be checked Edge to be detected Ud Vd Wd Leading edge Ud— H L Vd L — H Wd H L — Trailing edge Ud — L H Vd H — L Wd L H —

In FIG. 12, the leading edge of the spike voltage Ps starting from theelectrical angle θ1 is masked, but the trailing edge of the same spikevoltage Ps cannot be masked; therefore, a check is made to confirmwhether the conditions of trailing edge shown in Table 2 and Table 3 aresatisfied or not. In this case, the conditions for the induced voltagesignal Ud of the trailing edge of Table 3 are satisfied; therefore, itcan be treated as being the edge of the spike voltage Ps. This signal isremoved, and the position detection signal Us is generated. The edge ofthe electrical angle θ2 satisfies the conditions of Table 2 as mentionedabove, so it is taken as the induced voltage edge. Similarly, thetrailing edge of the spike voltage Ps that starts from the electricalangle θ3 is removed by the mask signal Um. The leading edge of the samespike voltage Ps satisfies the conditions related to the induced voltagesignal Ud of the leading edge of Table 3, therefore, it is also removed.In this way, when a pulse of the spike voltage Ps that cannot be removedby the mask signal Um exists, the high and low voltage levels of otherinduced voltage signals Vd, Wd are examined and the necessity forremoval is judged by checking the conditions of Table 2 and Table 3.Then the signal due to the spike voltage Ps is removed and the positiondetection signal Us is generated. In a similar manner, the positiondetection signals Vs and Ws are generated.

Next, the processing by the stop processing unit 124 of the controlapparatus 110 is described here.

As shown in FIG. 13, when the load on the brushless motor 1 is graduallyincreased, overload state of the brushless motor 1 is judged in thisprocessing, and the brushless motor 1 is stopped. The processing isdivided into two cases and described here: the case when the pulse ofthe spike voltage Ps in the steady state is changed from the maskablestate to the load-increase state (load judgment D1) by the mask width ofthe mask signals Um, Vm, Wm generated by the mask signal generation unit126, and the case when the pulse of the spike voltage Ps in the steadystate is changed from the state where it cannot be masked to theload-increase state (load judgment D2).

First, the load judgment D1, that is, when the pulse width of the spikevoltage Ps in the steady state is less than the mask width, the stopprocessing unit 124 judges by assuming the mask width as the thresholdof the overload judgment. More specifically, when a pulse of the spikevoltage exists that cannot be removed by the mask signals Um, Vm, Wm,the edge separation processing unit 122 hands over this signal to thestop processing unit 124. It is not clear whether such a pulse is due tothe spike voltage Ps, or to the induced voltage; therefore, judgment ismade by examining whether the conditions of Table 3 are satisfied ornot. The result is that if the conditions of Table 3 are satisfied andit is clear that the signal is the edge of the spike voltage Ps, thenthe state is treated as the overload state. Consequently, the stopprocessing unit 124 outputs the command signal to stop to the energizingcurrent timing switching generation unit 125, and the brushless motor 1is stopped.

In contrast, the load judgment D2, that is if the pulse width of thespike voltage Ps in the steady state exceeds the mask width, the stopprocessing unit 124 judges the specified electrical angle 1 as thethreshold value of the overload judgment. Here, for the specifiedelectrical angle R1, the value set beforehand corresponding to thephysical frame of the brushless motor 1 or the inertia load may be used,for example, a value of 360° may be set. As shown in FIG. 13,originally, when the induced voltage edge realized periodically cannotbe detected by the rotor position detecting unit 123, the stopprocessing unit 124 examines the counter value that is reset each timethe induced voltage edge is detected. The result is that the even if thecounter value exceeds the value corresponding to the electrical angleR1, as long as it is not reset, the state will be treated as theoverload state. Consequently, the stop processing unit 124 outputs thecommand signal to stop to the energizing current timing switchinggeneration unit 125, and the brushless motor 1 is stopped.

According to this embodiment, the energizing current switching timing iscalculated after detecting the induced voltage, and by feedback of thisenergizing current timing, the mask signals Um, Vm, Wm for masking thespike voltage Ps are generated. Therefore, regardless of the existenceof the spike voltage Ps, the mask signals Um, Vm, Wm can always begenerated. Consequently, even if the spike voltage Ps is generated atthe stage when switching of the energizing current is repeated, theposition of the rotor 6 can be accurately detected. Thus, the energizingcurrent can be switched at the appropriate timing without depending onthe type of the brushless motor 1 or the loading condition. Also, thereis no need to install an external digital masking circuit separately formasking, therefore, the scale of the circuit can be made smaller.

In the embodiment described above, as a measure against the widevariation in the pulse width of the spike voltage during load variation,an advance angle correction device may be added to the control apparatus110. The advance angle correction device subtracts the period ofswitching the energizing current from the pulse width of the spikevoltage, and takes half the subtracted value as the advance anglecorrection value. The energizing current timing generation processingunit 125 takes the position detection signals Us, Vs, Ws, advanced onlyby the advance angle correction value as the position detection signalsUss, Vss, Wss, and controls the switching of the energizing currentbased on these signals.

The present invention is not limited by the embodiments described above,and appropriate changes may be effected to the present invention withoutdeparting from the spirit and scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be applied to control apparatus, and controlmethod and motor system of brushless motors, without installing aspecial sensor in the brushless motor and to perform stable control ofthe energizing current.

1. A brushless motor control apparatus comprising: a drive circuit forobtaining a rotating magnetic field by energizing a plurality of statorcoils disposed so as to apply a rotating magnetic field to a rotorhaving permanent magnet and for sequentially switching the currentenergizing the stator coil based on the position detection signalobtained by comparing the change in the induced voltage generated in thestator coil not energized by rotation of the rotor and the standardvoltage; and a timing varying circuit for changing the timing to switchthe current energizing the stator coil according to the pulse width ofinduced voltage generated in the stator coil immediately after switchingthe current energizing the stator coil.
 2. The brushless motor controlapparatus according to claim 1 wherein timing for switching currentenergizing the stator coil is advanced only by half the pulse width ofspike voltage generated due to flywheel current.
 3. A motor systemcomprising the brushless motor control apparatus according to claim 1,and a brushless motor controlled by the brushless motor controlapparatus.
 4. A brushless motor control method comprising: obtaining arotating magnetic field by energizing a plurality of stator coilsdisposed so as to apply a rotating magnetic field to a rotor havingpermanent magnet; sequentially switching the current energizing thestator coil based on a position detection signal obtained by comparingthe change in induced voltage generated in the stator coil not energizedby rotation of the rotor and the standard voltage; and changing thetiming to switch the current energizing the stator coil according to thedifference in the energizing current switching interval for the statorcoil and the pulse width of induced voltage generated in the stator coilimmediately after switching the current energizing the stator coil. 5.The brushless motor control method according to claim 4 furthercomprising obtaining the difference by stopping measurement for only aperiod equivalent to the pulse width of the induced voltage generated inthe stator coil immediately after switching the current energizing thestator coil when the energizing current switching interval of the statorcoil is measured.
 6. A brushless motor control apparatus comprising: adrive circuit for obtaining a rotating magnetic field by energizing aplurality of stator coils disposed so as to apply a rotating magneticfield to a rotor having permanent magnet and for sequentially switchingthe current energizing the stator coil based on a position detectionsignal obtained by comparing the change in induced voltage generated inthe stator coil not energized by rotation of the rotor and the standardvoltage; and a mask signal generation unit for generating mask signalbased on the position detection signal to mask the change in voltagegenerated in the stator coil immediately after switching the currentenergizing the stator coil.
 7. The brushless motor control apparatusaccording to claim 6 wherein the mask signal is generated beforeswitching the current energizing the stator coil.
 8. The brushless motorcontrol apparatus according to claim 6 wherein the pulse width of themask signal is a fixed electrical angle.
 9. A motor system comprisingthe brushless motor control apparatus according to claim 6, and abrushless motor controlled by the brushless motor control apparatus. 10.A brushless motor control method comprising: obtaining a rotatingmagnetic field by energizing a plurality of stator coils disposed so asto apply a rotating magnetic field to a rotor having permanent magnet;sequentially switching the current energizing stator coil based on aposition detection signal obtained by comparing the change in inducedvoltage generated in the stator coil not energized by rotation of therotor and the standard voltage; and generating mask signal based on theposition detection signal and for masking change in voltage generated inthe stator coil immediately after switching current energizing thestator coil.